- Published on
Anthropic watermarks all Claude outputs globally with marks that 'may persist through some editing'
- Authors
- Name
- DeepHorus
Anthropic has signed the EU AI Act Code of Practice and will watermark all Claude outputs globally starting in August 2026. New Claude models launched in the EU on or after August 2, 2026, will embed invisible watermarks in text and attach signed provenance metadata to files. The requirement covers the API, Claude, Claude Code, Claude Cowork, and Claude Tag worldwide.
The company uses two labeling methods. Text receives an invisible watermark that does not affect quality and "may persist through some editing." Supported images like .svg, .png, and .jpg get C2PA-standard signed metadata to verify Claude processed the file.
Existing models will be retrofitted during a transition period. The watermark is applied at the model level, so it works across all products and cloud partners like AWS, Google Cloud, and Microsoft Foundry, though those platforms may not support signed metadata. Anthropic plans to release verification tools but has not set a date.
The company acknowledges limits. A watermark does not prove Claude wrote the content, since people use the AI to edit or translate their own text. A missing watermark does not confirm human authorship either, because heavy editing, format conversion, or short passages can strip or obscure the signal.
This places Anthropic alongside Google DeepMind, which open-sourced SynthID in Gemini, and OpenAI, which has reportedly built a detector with 99.9 percent accuracy but has not released it. Third-party detectors could adopt Anthropic's watermark as a more reliable signal than proprietary systems like Pangram. Developers integrating Claude must determine which Article 50 requirements apply to them.
The real test is whether the watermarks survive editing, translation, and reformatting. If they hold up, they may become a widely accepted standard for identifying AI-generated content. Until then, detection remains an open and contested issue across society.
